Multi-floor semiconductor fabrication plants are commonplace, especially in Asia, where real estate is scarce. Thus, an interfloor transport system is required to move items between floors. Generally, an interfloor transport system must penetrate one or more fire isolation zones, which are solid concrete or masonry floors or ceilings, in the building. Building codes generally require that any floors within fabrication or hazardous material production areas be separated from each other by not less than one-hour fire resistive occupancy separations.
Vertical fire shafts and vertical fire doors are commonly used in fabrication areas where interfloor transport devices penetrate a fire zone floor. Vertical fire doors, which are required in every location where access is needed to the equipment within, typically generate particulates that can be difficult to remove or control in an environment that requires a high degree of cleanliness, such as semiconductor fabrication. Also, vertical fire doors must be fully cleared of people and equipment before they can be closed. The vertical shafts must also be large enough for personnel to enter for maintenance and repair tasks. Consequently, the vertical shafts require a large amount of floor space.
The elevator assembly within the shaft typically includes bearings and tracks or rails on the sides of the shaft and cabling in the middle of the shaft. A horizontal door cannot readily seal around such a dispersed arrangement of equipment. Horizontal openings through floors, if used at all, must be fully cleared of the transport system and payload before the opening can be sealed with a horizontal door.
The present invention relates to a horizontal door system for use in conjunction with an interfloor transport or elevator system installed through a horizontal opening in a floor or ceiling. The interfloor transport system includes a drive column incorporating tracks or guide rails on which a robot assembly rides. Accordingly, the tracks are located in an area generally closer to the cabling attached to the robot assembly than in prior art elevator assemblies. The drive column has an irregular profile formed by vertical elements that define a fixed horizontal cross-section within the opening. The horizontal door system is able to seal around the irregular profile of the drive column and any cabling present in the opening. The horizontal door system is particularly useful as a fire door separating fire zones. The door system is also capable of sealing off the fire zones even if equipment is present in the penetration in the floor.
In a preferred embodiment, the door system comprises an upper door assembly that closes the opening in the floor, a lower door assembly suspended below the floor, and an interconnecting plenum. The height of the interconnecting plenum between the upper and lower door assemblies is selected to be larger than the height of the equipment that travels along the drive column and any loop formed by the cabling. Thus, even if equipment were present within the opening in the floor during a fire emergency, the lower door assembly would be clear of any obstructions and could be closed, sealing the interior of the plenum and the upper zone from the lower zone. In addition, the upper and lower door assemblies preferably include an expandable intumescent fire sealing or gasketing material that seals around the drive column and the cabling if present within the opening.
In operation as a fire door system, the door system remains open under normal conditions and closes automatically when a selected condition is detected, such as an increase in temperature above, for example, 165xc2x0 F., actuation of a smoke detector, or actuation of a fire alarm device. The fire door system is capable of limiting the passage of fire and smoke and the temperature rise across the horizontal surface for a predetermined period of time, for example, two hours for hazardous material production areas.